a standard time used in the zone which includes Hawaii and the western Aleutian Islands, corresponding to the mean solar time of the 150th meridian west of Greenwich, England: it is ten hours behind Greenwich time
See Hawaii-Aleutian Standard Time in American Heritage Dictionary 4
noun
Standard time in the tenth time zone west of Greenwich, England, reckoned at 150° west and used, for example, in Hawaii and the western Aleutian Islands.